The winter duke
(Book)

When Ekata's brother is finally named heir, there will be nothing to keep her at home in Kylma Above. Not her books or science experiments, not her family's icy castle atop a frozen lake, not even the tantalizingly close Kylma Below, a mesmerizing underwater kingdom that provides her family with magic. But just as escape is within reach, her parents and twelve siblings fall under a sleeping sickness. Ekata inherits the title of duke, her brother's warrior bride, and ever-encroaching challengers from without-- and within. If Kylma Above is to survive, Ekata must seize her family's magic and power-- and decide how she will wield them. -- adapted from jacket

Ages 14+.,Little, Brown and Company.